The present invention relates generally to data processing arrangements and, more particularly, to the processing of scalable data in a multimedia system where more than one data source transmits over a common communication channel.
The widespread use of digital processing technology has found its way into a variety of equipment and, in some form, into most industries. In many applications involving communication of different types of information, data processing arrangements have been configured to multiplex information from each type of information source over various communication-media types and arrangements.
In a typical multimedia application, for example, one type of data processing arrangement permits several data sources to transmit data over the same communication channel. In this environment, a multiplexing arrangement is typically used to process certain types of data from each of the several data sources and to present this processed data to the communication channel transmission equipment in an orderly fashion. The multiplexing arrangement receives an input from each data source and, through a single output port, provides the data to the communication channel according to a preestablished multiplexing protocol.
A problem arises, however, when attempting to efficiently use such a shared communication channel. The various data sources at the input side of the multiplexer provide data at varying rates based on the particular applications served by the data sources. The data transmission equipment, at the other side of the multiplexer, typically includes a specific maximum data transmission bandwidth that permits the transmission of data up to a certain upper limit. If the preestablished multiplexing protocol effects data collection from each of the data sources according to a specified rate, the multiplexer often fails to process enough data from some data sources. Moreover, the multiplexer often fails to process any data from other data sources. Such data processing failures render approaches of this type unacceptable for many data processing applications.
One approach to dealing with this problem involves using a relatively large stack data register arrangement, such as a first-in-first-out (FIFO) memory circuit, at each of the inputs to the multiplexer and at the output of the multiplexer. Using this arrangement, the multiplexer can draw data from each of the FIFOs at the input side and provide valid data to the FIFO at the output such that the output FIFO always contains data ready for transmission. The data transmission equipment will virtually always be filling its channel bandwidth by constantly drawing valid data from the output FIFO. One drawback of this method is that each FIFO introduces a delay in processing the data from the input source through to the transmission channel.
Another approach to this problem involves implementing one of the input data sources, such as a video encoder, using an internal mechanism that scales its output data rate by adjusting the amount of distortion in the encoded video signal. In approaches of this type, the multiplexer typically attempts to track the available bandwidth according to the amount of data in the output buffer of the video encoder. With the multiplexer drawing data from the FIFO of the video encoder according to available channel bandwidth, the video encoder decreases its data rate when the output buffer level rises and increases its data rate when the output buffer level drops. This approach, however, requires that the video encoder maintain a nominal or quiescent buffer level, thereby introducing undesired and often unacceptable delay. Another drawback to this approach is that the video encoder lacks direct access to the data rates of the other data sources, which together with the characteristics of the transmission determine the available channel bandwidth. Thus, the video encoder has to wait for changes in the data rates of the other data sources to affect the video encoder output buffer level. This delay reduces the speed at which the video encoder can adapt to these changes. Moreover, this approach often results in sudden changes in the output data rate of the video encoder. Sudden changes of this type can cause sudden changes in coding distortion, which adversely affect the perceived video quality.
Accordingly, a need exists for an improved data processing arrangement and method thereof for efficiently transmitting data in a manner that overcomes the above-mentioned shortcomings.
According to a system implementation of the present invention, a multimedia communication arrangement includes an image collecting terminal, a modem, and a data recovery terminal. Video and other signal types are processed by the image collecting terminal for transmission through a modem over a communication channel to a data recovery terminal. The system includes a first data source including a video image processor constructed to capture images and to present the images as a first type of data at a rate that varies in response to an available bandwidth factor for the communication channel. At least one additional data source generates at least one additional data signal. A data signal processing circuit is configured and arranged to collect the first type of data from the first data source at a rate that varies in response to an available channel bandwidth of the modem, to collect at least one additional type of data from the at least one additional data source at at least one established rate, and to adjust a transmission rate of the modem in response to a detected error rate.
According to another embodiment of the present invention, a multimedia communication system can be used to transfer video and other signal types from an image collecting terminal to a modem for transmission over a communication channel to a data recovery terminal. A first data source including a video image processor captures images from a video camera and presents them as a first type of data at a rate that varies in response to an available bandwidth factor for the communication channel. At least one additional data source generates at least one additional data signal. A data signal processing circuit is configured and arranged to collect the first type of data from the first data source at a rate that varies in response to an available channel bandwidth of the modem, to collect at least one additional type of data from the at least one additional data source at at least one established rate, and to adjust an amount of filtering performed by the video camera.
Another aspect of the present invention is directed to a multimedia communication terminal, comprising a first data source that includes a video image processor. The video image processor is constructed to capture images from a video camera and to present the images as a first type of data at a rate that varies in response to an available bandwidth factor for the communication channel. A second data source generating audio data. A data signal processing circuit is configured and arranged to collect the first type of data from the first data source at a rate that varies in response to an available channel bandwidth of the modem, to collect the audio data, and to delay delivery of the audio data to the modem.
Yet another aspect of the present invention is directed to a method for formatting multiple types of data, including data representing images, for transmission over a communication channel using a modem. Captured images are presented as a first type of data at a rate that varies in response to an available bandwidth factor for the communication channel. At least one additional data signal is generated. The first type of data is collected at a rate that varies in response to an available channel bandwidth of the modem. The at least one additional data signal is collected at at least one established rate. A multiplexing arrangement is configured and arranged to detect an error rate. A transmission rate of the modem is adjusted in response to the detected error rate.
According to still another embodiment of the present invention, formatting of multiple types of data for transmission over a communication channel using a modem is accomplished by presenting images captured using a video camera as a first type of data at a rate that varies in response to an available bandwidth factor for the communication channel. At least one additional data signal is generated. The first type of data is collected at a rate that varies in response to an available channel bandwidth of the modem. The at least one additional data signal is collected at at least one established rate. An amount of filtering performed by the video camera is adjusted.
Yet another embodiment of the present invention is directed to a method for formatting multiple types of data for transmission over a communication channel using a modem. The method includes presenting images captured using a video camera as a first type of data at a rate that varies in response to an available bandwidth factor for the communication channel. An audio data signal is generated. The first type of data is collected at a rate that varies in response to an available channel bandwidth of the modem. The audio data is also collected. Delivery of the audio data to the modem is delayed.
The method embodiments described above can also be implemented using systems. The above summary of the invention is not intended to describe each disclosed embodiment of the present invention. The figures and the detailed description will exemplify other aspects.